A carbon tax is a fee that governments place on the carbon content of fossil fuels or on greenhouse-gas emissions, designed to make polluting activities more expensive and thereby encourage households and businesses to cut emissions and shift toward cleaner alternatives.
As countries search for ways to reduce greenhouse-gas emissions, one policy comes up again and again: putting a price on carbon. A carbon tax is the most direct version of that idea. It rests on a simple economic logic, that if something is made more expensive, people tend to use less of it. This explainer covers what a carbon tax is, how it works in practice, how it compares with cap-and-trade, and what happens to the money it raises.
What is a carbon tax?
A carbon tax is a charge on greenhouse-gas emissions, most commonly priced per tonne of carbon dioxide, or carbon-dioxide equivalent for other gases. In many designs the tax is applied to fossil fuels according to how much carbon they contain, so coal, oil, and natural gas become more expensive to burn in proportion to the emissions they produce.
The underlying idea is that emissions carry a cost to society, through their contribution to climate change, that is not reflected in the market price of fuel. Economists call this an “externality.” A carbon tax is intended to internalise that cost, putting a visible price on something that was previously free to emit. This connects to the wider difficulty of global climate action explored in our piece on why climate diplomacy keeps stalling.
How does it actually work?
In practice, a carbon tax sends a price signal through the economy. When fossil fuels cost more, the effects ripple outward: electricity generated from coal or gas becomes pricier, as does petrol and diesel, and so do goods and services that rely heavily on energy. Faced with those higher costs, businesses and households have an incentive to change behaviour, by improving efficiency, switching to lower-carbon energy, or reducing consumption.
A defining characteristic of a carbon tax is price certainty. The government sets the price per tonne, so emitters know what carbon will cost. What the tax does not do is guarantee a specific level of emissions reduction; the market decides how much to cut in response to the price. This is the mirror image of the main alternative, cap-and-trade.
Where the tax is applied also matters. Many carbon taxes are collected “upstream,” at the point where fuels enter the economy, such as at refineries, mines, or import terminals, which keeps the number of taxpayers manageable and lets the cost flow through the supply chain. Others are applied closer to the point of use. Designers must also decide which sectors and gases to cover, whether to phase the price in gradually, and how to treat industries exposed to international competition, all of which affect how much the tax reduces emissions and how it is felt across the economy.
How does a carbon tax compare with cap-and-trade?
Carbon taxes and cap-and-trade systems, also called emissions trading systems, are the two dominant approaches to carbon pricing. They aim at the same goal but pull different levers.
| Feature | Carbon tax | Cap-and-trade |
|---|---|---|
| What is fixed | The price per tonne of emissions | The total quantity of emissions allowed |
| What the market sets | The amount of emissions reduced | The price of emission allowances |
| Certainty offered | Price certainty for emitters | Certainty about the emissions total |
| How it operates | A direct fee on carbon | Trading of a limited number of permits |
In short, a carbon tax fixes the price and lets emissions adjust, while cap-and-trade fixes the quantity of emissions and lets the price adjust through trading. Each has advocates, and some jurisdictions use elements of both. The choice often comes down to whether policymakers prioritise predictable prices or a guaranteed emissions ceiling.
What happens to the revenue?
One of the most consequential questions about any carbon tax is what governments do with the money it raises, because that choice shapes both its fairness and its political durability. There are several common approaches. Revenue can be returned directly to the public as rebates or “dividends,” so that households receive a payment that offsets higher energy costs. It can be used to reduce other taxes, an approach sometimes called a revenue-neutral carbon tax. Or it can fund public spending, such as clean-energy investment, public transport, or support for affected communities.
These choices matter because a carbon tax can raise the cost of energy and everyday goods, which can weigh more heavily on lower-income households that spend a larger share of their budgets on essentials. Returning revenue to households is one way designers try to address that concern. Because the effects touch personal budgets, this overlaps with broader household money and economy questions, though how any individual is affected depends on their own energy use and the specific policy.
How widespread is carbon pricing?
Carbon pricing is no longer a fringe idea. According to analysis by the OECD, carbon taxes and emissions trading systems have been adopted across dozens of jurisdictions worldwide, and together they now cover a meaningful share of global greenhouse-gas emissions. Carbon taxes and trading systems each account for a portion of that coverage, with trading systems generally covering a larger slice of emissions than taxes.
That said, the picture is uneven. Prices differ enormously from one system to another, coverage varies by sector, and many emissions worldwide still carry no explicit price at all. Whether carbon pricing is set high enough, applied widely enough, and paired with the right complementary policies remains a live debate among economists and policymakers. What is clear is that the carbon tax has moved from theory to a widely used, if contested, tool, and understanding how it works is essential to following climate politics and policy around the world.
Frequently asked questions
What exactly does a carbon tax charge?
A carbon tax places a price on greenhouse-gas emissions, usually measured per tonne of carbon dioxide or its equivalent. In practice it is often applied to fossil fuels based on their carbon content, so coal, oil and gas cost more to burn.
How is a carbon tax different from cap-and-trade?
A carbon tax sets the price of emissions and lets the market determine how much gets reduced. Cap-and-trade sets a limit on total emissions and lets the market set the price through the trading of allowances. One fixes price, the other fixes quantity.
What happens to the money raised?
That depends on the government. Revenue can be returned to households as rebates or dividends, used to cut other taxes, or spent on clean-energy and public programmes. The choice of what to do with the revenue is a central policy debate.
Does a carbon tax raise consumer prices?
It can, because higher costs for fossil fuels may pass through to energy, transport and goods. Some designs offset this by returning revenue to households. The net effect on any individual depends on their energy use and the specific policy design.
How widely is carbon pricing used?
Carbon pricing has spread to dozens of jurisdictions worldwide through both carbon taxes and emissions trading systems. According to OECD analysis, together these instruments cover a significant share of global emissions, though coverage and price levels vary a great deal.
